This invention relates to a process for recovering in situ both petroleum and minerals from an oil shale deposit.
Oil shale deposits in Colorado and Wyoming have been well known for over fifty years. The Green River Formation, covering an area of approximately seventeen thousand square miles in south-western Wyoming, north-eastern Utah and north-western Colorado, has oil shale deposits with total oil resources estimated to be eight trillion barrels of oil in oil shales containing over ten gallons of oil per ton. The Piceance Creek Basin alone, in Colorado, has deposits containing 1.2 trillion barrels of oil in oil shales having oil content of over fifteen gallons per ton. The amount of oil in this formation alone is sufficient to supply the United States with oil for approximately one hundred thirty years, assuming a consumption of twenty-five million barrels per day.
However, recovery of the petroleum from these enormous deposits has never been economical. Even after the huge recent increases in oil prices on the world market, the projected costs for recovering from this shale has remained higher than the costs of purchasing the oil in the world market.
An object of this invention is to make it economical to produce oil from shale deposits. This object can be achieved according to the present invention by a long-term process in which inorganic minerals are also recovered by solution mining and by linking the various processes together.
The practice of solution mining in situ of oil shale deposits has been previously proposed. The prior-art has proposed both leaching after retorting (e.g., Prats U.S. Pat. No. 3,502,372 and Garret U.S. Pat. No. 3,661,423) and leaching before retorting (e.g., Papadopoulos et al U.S. Pat. No. 3,700,280, Beard U.S. Pat. Nos. 3,759,574, 3,779,601 and 3,779,602, Closmann et al, U.S. Pat. Nos. 3,945,679, 3,957,306, and 3,967,853, Pearson et al U.S. Pat. No. 4,059,308, Hill et al U.S. Pat. No. 4,065,183, and Bohn et al U.S. Pat. No. 4,083,604. Various methods for solution mining have been proposed in these patents: injections of steam, hot-water, aqueous solutions of lye or lime, aqueous acid solutions, and so on.
However, these patents evince no interest in or processes for recovering the inorganic mineral values; they relate only to creating voids in the shale. Little, if anything, has even been said about possible recovery of the mineral values, and nothing has been said about how recovery is feasable.
The Piceance Creek Basin formation, in addition to its petroleum values, also contains the locally abundant, but otherwise rare minerals nahcolite, NaHCO.sub.3 and dawsonite, NaAl(OH).sub.2 CO.sub.3, both in large quantities. The reserve of these minerals in the Piceance Creek Basin is estimated to be: thirty billion tons of nahcolite and twenty-two billion tons of dawsonite. Similarly, in Utah and Wyoming the shale contains large amounts of trona, Na.sub.2 CO.sub.3.NaHCO.sub.3.2H.sub.2 O, and other minerals.
The nahcolite can be converted to soda ash (Na.sub.2 CO.sub.3) and/or caustic soda (NaOH). The stoichiometric equivalent of 30 billion tons of nahcolite (NaHCO.sub.3) is 18.9 billion tons of Na.sub.2 CO.sub.3, or 14.3 billion tons of NaOH, or any combination of the two.
The dawsonite can be decomposed, and the individual products of decomposition recovered. The stoichiometric equivalent of 22 billion tons of dawsonite, NaAl(OH).sub.2 CO.sub.3 is 8.1 billion tons of Na.sub.2 CO.sub.3, or 6.1 billion tons of NaOH, or any combination of the two, plus 7.8 billion tons of alumina (Al.sub.2 O.sub.3), or 4.1 billion tons of aluminum, or any combination of the two. The aluminum contained in this deposit of dawsonite is sufficient to supply the aluminum needs of the United States for several hundred years, and could eliminate dependence on imported raw materials.